Heads turned, the sermon stopped abruptly and the Rev. Wassem Sabeeh quietly began ushering parishioners into a fortified room in the rear of the church.

"We realized these explosions were close," said Bassam Sami, 21, one of the survivors of the attack on a Baghdad church carried out by heavily armed suicide bombers that left at least 58 people dead. "Father Wassem started pushing people inside the room."

Once they penetrated the church building, the silent assailants began executing people. "They were well trained," Sami said. "They didn't say anything. It was like someone had cut out their tongues."

The carnage that unfolded during the next few hours outraged many in a city that has seen more than its share of bloodshed. The siege suggested that al-Qaeda in Iraq, the weakened Sunni insurgent group that asserted responsibility for the attack, remains capable of carrying out mass-casualty operations.

The target, an Assyrian Christian church in the upscale Karrada neighborhood, was highly unusual. The extremist group has in the past year directed its dwindling resources toward crippling symbols of the Shiite-led Iraqi government.

An Iraqi official said Monday that investigators had found at the scene three Yemeni and two Egyptian passports thought to have belonged to the suicide bombers. If confirmed, the finding would be alarming to U.S. and Iraqi officials because they say al-Qaeda in Iraq has struggled to recruit foreign fighters in recent years.

In a statement posted on the Internet early Monday, the Islamic State of Iraq, a front group for al-Qaeda in Iraq, asserted responsibility for the attack.

It said the attackers were motivated by the reported abduction of Muslim women by Catholic Church officials in Egypt. The statement appeared to allude to the disappearance of the wife of a Coptic Church priest in Cairo. Muslim protesters in the Egyptian capital have accused church officials of abducting the woman after she voluntarily converted to Islam.

Church officials have denied the allegation. The case has received heavy media coverage in Egypt, where Coptic Christians make up about 10 percent of the population. Clashes between Muslims and Christians have erupted there sporadically in recent years.

Before Monday, the controversy had gone largely unnoticed in Iraq, where most headlines these days are about stalled negotiations to form a government after the March 7 parliamentary elections.

It is not clear why the assailants chose to make the prominent Iraqi church a battleground in the case of the missing woman.